In general, most pylon-mounted jet engine nacelles, whether mounted on the wing or fuselage, have numerous panels or cowlings that can be opened to gain access to the engine and its accessories. They are typically light-weight, contoured panels of sheet-metal construction that are pivotally attached to the nacelle structure or pylon. Usually, manually extendable support rods are provided to hold the cowling in the open position. If the cowling is large, and/or the weight of the cowling is high, an opening and closing hydraulic actuation system may be incorporated. A typical hydraulic system for opening and closing cowling on a jet engine nacelle can be found in U.S. Pat. No. 4,399,966, "Power Opening System for Engine Cowl Doors" by E. H. Cruden et al. In this system, each cowling section is controlled by a separate hydraulic actuator.
On aircraft such as the McDonnell Douglas DC-10, with high-bypass ratio fan-jet engines, the thrust reversers are mounted in the fan duct. In such engine and nacelle combinations, the thrust reversers are sometimes incorporated into the engine access cowling. For example, in U.S. Pat. No. 3,541,794, "Bifurcated Fan Duct Thrust Reverser" by E. A. Johnson et al., the thrust reversing mechanisms are in cowling halves hingeably connected to the engine pylon. These cowling/thrust reverser combinations weigh in at several hundred pounds. Since they are hinged at the top of the nacelle and rotated outward and upward to obtain access to the engine, non-assisted opening is difficult to accomplish. Thus, a hydraulic actuation system of the type previously mentioned is incorporated. Combining the cowling and thrust reverser into one assembly has significant advantages, mainly a weight reduction and ease of maintenance.
This particular design is readily adaptable to an under-wing mounted engine or one mounted in the tail of an aircraft. If, however, the engine and nacelle are mounted to the side of the fuselage by means of a pylon, such as on the McDonnell Douglas DC-9 or the Boeing Aircraft Corporation 727, it is not possible to provide cowling which opens on the side of the engine next to the fuselage due to interference therewith. Additionally, a hydraulic system of the type as set forth in U.S. Pat. No. 4,399,966, "Power Opening System for Engine Cowl Doors" by E. H. Crudden et al. now becomes quite large and heavy, in that each hydraulic cylinder must react the total weight of the cowling half.
Therefore, it is a primary object of the subject invention to provide a system for opening and closing cowling sections mounted about a jet engine and nacelle therefor which are pylon mounted to the fuselage of the aircraft.
It is another object of the subject invention to provide a powdered system for simultaneously opening engine nacelle cowling sections upward and downward to obtain access to the engine and its accessories.
It is a further object of the subject invention to provide a cowling assembly wherein the weight of the power system used to open and close the cowling sections is at a minimum.
It is a still further object of the subject invention to provide a cowling assembly wherein cowling sections are counterbalanced.